Spinal cord stimulation is a well accepted clinical method for reducing pain in certain populations of patients. Implantable stimulation devices have been developed to provide therapy for a variety of treatments. For example, implantable stimulation devices can be used to stimulate nerves, such as the spinal cord, muscles, or other tissue. An implantable stimulation device typically includes an implanted control module (with a pulse generator), a lead, and an array of stimulator electrodes. The stimulator electrodes are implanted in contact with or near the nerves, muscles, or other tissue to be stimulated. The pulse generator in the control module generates electrical pulses that are delivered by the electrodes to body tissue. As an example, electrical pulses can be provided to the dorsal column fibers within the spinal cord to provide spinal cord stimulation.
The stimulator electrodes are coupled to the control module by the lead and the control module is implanted elsewhere in the body, for example, in a subcutaneous pocket. The lead is often anchored at one or more places in the body to prevent or reduce movement of the lead or stimulator electrodes within the body which could damage tissue, move the stimulator electrodes out of the desired position, or interrupt the connection between the stimulator electrodes and the control module.
Many conventional lead anchors possess inadequate lead retention strength when the lead is subjected to tensile loading. This may cause the lead to migrate proximally from the desired neurostimulation site. According to recent studies, lead migration occurs in approximately 13% of cases. Additional studies suggest that electrode migration may be the most common reason for failure to maintain long-term pain control with spinal cord stimulation. Other problems associated with lead migration include lead breakage, and loose connection.
Yet another problem associated with conventional lead anchors is that they typically contain moving, multi-part mechanisms or locks that could unintentionally disengage after implantation. The added complexity may cause lead migration and breakage as explained above.